With the socio-economic development and the improvement of material living standards, the number of diabetics on a global scale is increasing rapidly. Diabetes is usually divided into two types, such as type I and type II, in which more than 90% of diabetes is type II. Many types of diabetes drugs are already commercially available, but so far no drug has been able to single-handedly keep the blood glucose levels of patients with type II diabetes within the target range for a long time. In recent years, more and more approaches for the treatment of type II diabetes are provided due to the in-depth study of the pathogenesis of diabetes. The discovery of sodium-glucose cotransporter 2 (SGLT-2) inhibitors provides another new idea for the treatment of diabetes. The mechanism of action of SGLT-2 inhibitors is to selectively inhibit the activity of SGLT-2, thereby reducing blood glucose. SGLT-2 is selected as a target spot, on one hand because of its absolute reabsorption of glucose, and on the other hand because it is only expressed in the kidney. The current study also finds that the mechanism of action of SGLT-2 does not depend on the dysfunction of β cells or the degree of insulin resistance, and its effect is not decreased with function failure of β-cell or severe insulin resistance. Therefore, it is reasonable to believe that the use of SGLT-2 inhibitors in the current treatment of type II diabetes has a promising future.
WO2012019496 discloses a SGLT-2 inhibitor having the following formula, whose chemical name is 1,6-anhydro-1-C-{4-chloro-3-[(3-fluoro-4-ethoxyphenyl)methyl]phenyl}-5-C-(hydroxymethyl)-β-L-idopyranose.

However, it is impractical to directly use 1,6-anhydro-1-C-{4-chloro-3-[(3-fluoro-4-ethoxyphenyl)methyl]phenyl}-5-C-(hydroxymethyl)-β-L-idopyranose as a pharmaceutically active ingredient due to its poor development form resulting from the lower melting point (83° C.) and hygroscopic properties. Therefore, it is important to develop a stable form of the compound.
The crystal structure of the pharmaceutically active ingredient often affects the chemical stability of the drug. Different crystallization conditions and storage conditions may lead to changes in the crystal structure of the compound, and sometimes may be accompanied with the production of other crystal forms. In general, an amorphous drug product does not have a regular crystal structure, and often has other defects, such as poor product stability, smaller particle size, difficult filtration, easy agglomeration, and poor liquidity. Thus, it is necessary to improve the various properties of the above product. There is a need to identify a new crystal form with high purity and good chemical stability.